Bio lec

Overview of Major Elements in the Universe and Body Composition

  • The majority of elements in the universe, apart from helium, consist of four primary elements:
    • Oxygen
    • Carbon
    • Hydrogen
    • Nitrogen
  • These four elements account for 96.3% of the total body composition.
  • The remaining 4% of body composition includes:
    • Calcium
    • Phosphorus
    • Potassium
    • Sulfur
  • These elements are required by organisms in minute quantities.

Trace Elements

  • Discussion on essential trace elements, which include:
    • Iodine
    • Added to table salt by the government to ensure thyroid health.
    • Fluoride
    • Present in toothpaste for dental health.

Water and Oxygen Composition in the Body

  • Oxygen constitutes 65% of body weight, raising the question of how a gas contributes to this high percentage.
  • The explanation is provided through:
    • Water Composition
    • Water is comprised of two hydrogen atoms and one oxygen atom (H₂O).
    • Given that the molecular weight of oxygen is 16 and that of hydrogen is 1, the majority of the mass in water is attributed to oxygen.
    • Thus, the body being 65% oxygen can be understood primarily through its water content, which constitutes more than 60% of body weight.

Bone Composition and Toxicity of Elements

  • Additional elements in the body include:
    • Calcium
    • Phosphorus
    • Potassium
    • Sulfur
    • Sodium
    • Chlorine
    • Magnesium
  • Calcium and phosphorus predominantly reside in bones, accounting for about 99% of calcium and phosphorus in the body.
  • Introduction of toxic elements such as arsenic, which resembles phosphorus:
    • Arsenic leads to more brittle bones and is toxic to organisms.
  • Notably, some species adapt to environments with toxic elements, such as plants in serpentine soil which is considered toxic due to its acidity.

Atomic Structure and Properties

  • Atoms: Smallest unit of matter retaining properties of the element.
  • Subatomic Particles:
    • Neutrons: No charge, mass similar to protons.
    • Protons: Positive charge, mass equal to neutrons.
    • Electrons: Negative charge, significantly smaller mass (approximately 1/2000 of a neutron).
    • The total mass of an atom is predominantly from neutrons and protons.
  • Electrically Neutral Atoms: The number of protons equals the number of electrons.
  • Atomic Nucleus: Composed of protons and neutrons, whereas electrons form a negative cloud around it.
  • Atomic Number: Defined as the number of protons in the nucleus.
  • Mass Number: Total number of protons and neutrons in the nucleus.
  • Isotopes: Variants of the same element differing in neutron count.
    • Radioactive isotopes decay and are used in medicine for diagnostics, e.g., tracking metabolism in cancer patients.
  • Half-life: Time taken for the concentration of a radioactive isotope to decrease by half.
    • Varies from seconds to billions of years depending on isotope.

Energy Definition and Types

  • Energy: The capacity to cause change.
  • Two main types of energy:
    • Kinetic Energy: Energy in motion.
    • Potential Energy: Energy possessed by matter due to its position or structure (e.g., chemical bonds).
    • Matter tends to move towards its lowest potential energy state and this inclination is significant for understanding stability.
  • Electron Potential Energy: Electrons exist at various energy levels determined by their distance from the nucleus and can change levels by absorbing or releasing energy.
  • Representation of electrons is often simplified as being clustered in specific shells around the nucleus.
  • Chemical Behavior: Controlled by electron distribution; this distribution defines an atom's reactivity and bonds.

Chemical Bonds and Interactions

  • Valence Electrons: Electrons in outermost shell determining chemical behavior. Elements with complete valence shells are chemically inert (e.g., noble gases).
  • Covalent Bonds: Sharing of electron pairs between atoms, represented by solid lines in structural formulas.
    • Example:
    • Hydrogen Molecule (H₂): Two hydrogen atoms share electrons to fill their outer shells.
    • Methane (CH₄): Carbon shares electrons with four hydrogen atoms.
  • Electronegativity: Tendency of an atom to attract electrons; results in polar and non-polar covalent bonds:
    • Non-Polar Bonds: Equal sharing of electrons.
    • Polar Bonds: Unequal sharing, resulting in partial charges (δ+ and δ-).
  • Ionic Bonds: Form when atoms gain or lose electrons to become ions, leading to attractive forces between oppositely charged ions.
    • Example: Sodium and chloride form table salt (NaCl) through electron transfer.

Weak Chemical Interactions

  • Weak bonds play vital roles in biological systems, including:
    • Hydrogen Bonds: Result from polar interactions between molecules, significant for properties of water and structural integrity of proteins and DNA.
    • Discuss the importance of molecular shape, determined by atomic orbital hybridization, in biological recognition and function.
    • Example: Morphine's resemblance to natural endorphins allows it to bind to the same receptors, demonstrating the biochemical relevance of molecular shape.

Conclusion

  • Understanding atomic structure, energy types, and chemical bonds is essential for grasping core biological principles and how molecular interactions govern life processes.